Medallion etching process



Patented May 4, 19 26.

UNITE!) STATES PATENT OFFICE.

MURRAY C. IBEEBE, OI CINCINNATI, OHIO, ASSIGNOB TO THE WADSWOBTH WATCH CASE COMPANY, OF DAYTON, KENTUCKY, A CORPORATION OF KENTUCKY.

MEDALLION ETCHINC PROCESS. F

No Drawing.

To all whom it may concern:

'Beit known that I, MURRAY 0. Bnmm, a citizen of the United States, residing at Cincinnati, in the county of Hamilton and State of Ohio, have invented certain new and useful Improvements in Medallion Etching Processes, of which the following is a specification.

My invention relates to improvements in medallion etching process and it more especially consists of the features pointed out in the annexed claims.

The purpose of my invention is to provide a variable relief etching process that will enable one to produce medallion effects in high or low relief; that is simple in technique; that is also adaptable for machineor hand rotogravure; and that secures variable relief in lines stipple or other effects with a single etching solution'thus eliminating the usual graded etching methods in whlch varying strengths of mordant are used progressively.

With these and other ends in view, I instance such adaptations as will disclose the broad'underlying features of my invention without limiting myself to the specific details of procedure or exact proportion of parts described herein.

In practically carrying out my invention I may use any single layer coatlng which i when exposed to a luminous image will hecome variably permeable to a single etching solution. The original may have very deep shadows, brilliant highlights and graded middle tones or these tonal values may be accentuated or modified at will, though, what is known as a contrasty subject will, in the main be translated into a variable relief on metal better than so-called flat images.

In the well known photogravure process advantage is taken of the fact that a ferric chloride mordant, in a saturated solution will penetrate a gelatin coating, such as carbon tissue, with great difiiculty; and a diluted solution will penetrate such a coating more rapidly. In ordinary procedure four ferric chlorid solutions ranging from 32 to 40 .degrees Baum are used. The basic,

difference between the above described photogravure process and my method lies in Application fled January 19, 1928. Serial No. 613,758.

the fact that I take advantage of a uniiorm thickness film that is made variably per meable when exposed to a luminous Image, instead of producing a variable gelatin relief as is done in the usual photogravure or rotogravure processes. A further difference lies in my use of a single mordant with its attendant simplicity instead of several different etching solutions, each of which requires accurate timing with the risk of *completely spoiling the result, if the relation of the difi'erent etching stages are not properly maintained.

In the photogravure processes a grained surface in irregular or geometric pattern is used. The retention of such gram in the shadows is vitally necessary in order that the subsequent wiping ofi of surplus ink does not pull away the ink from the deep shadows. Similar surfaces may also be produced with my process but, asstated above, without the use of avariable relief or staged etching. a i

In case a matt surface relief is desired I may use an image that has its tonal gra ations broken up into half tone dots, vermicular or irregular grain areas without retaining these characteristics in the final relief etching. As the points of the grain are etched-away toward the end of the etching period a matt surface is produced. This procedure is specifically ada table to variable relief productions and o viously not to photogravure-purposes.

As an instance of adaptation the following steps of procedure and relation of ingredients is given. furfural acetone resin produces a suitable varnish. This is made by combining 50 grams of acetone, 62 grams of furfural with 100 cc. of a 50% solution of sodium hydrate and heating the mixture in a reflux condenser for about thirty minutes which produces a viscous-like varnish. Of this 12 grams is mixed with 3 grams of raw furfural.

and 5 cc. of alcohol. Inturn 20 cc. of this last mixture is combined with about 10 cc. of a 12 solution of iodoform to com stitute a light sensitive coating which is applied to the metal surface on which the vari- I have found that a able relief or other form of image is to be produced. The coating may be applied in any desired manner by brushing, whirling etc., etc, producing a so-called wet film onto which the desired image is impressed by means of optical projection for about ten minutes.

The image is developed in benzene and turpentine and is thereafter allowed to stand in turpentine to accentuate the selective permeability of the print corresponding to its more soluble portions. solubility and permeability are used synonomously inthe sense of a coating that 1s more or less porous and not in the sense of being dissolved away.

The etching may be done with a cyanide electrolyte when the image is formed on a gold surface and any other cooperating mordant when other metals are used. In the former case I have found that the permeability or the porosity of the furfural coating cooperates readily with well known gold etching solutions that contain a large amount of water. The image is approximately permeable in proportion to its varying luminosity. The deep shadows of the image or opaque portions of the negative or positive obviously constitute dark areas on the coating which remain in their original state. These areas being most permeable permit the mordant to commence etching the metal beneath the coating before other areas which have been made less permeable by the action of light. In other words the luminous portions of the image correspond to the.

shallowest parts of the variable relief and the highest relief to the darkest part of the image. I

A coating, after exposure, having the variable permeability characteristics above described is also amenable to a selective removal of such portions of the coating that have not been acted upon by the light by the use of any desired solvents or through the aid of mechanical abrasion, for instance, by means of finely powdered glass etc., in the etching bath which is delicately applied. However, in any event the resulting etching will be variable in relief in the same sense as when the coating is retained a uniform thickness. In either case the-action of the mordant is slowest where the light action has been the stron est.

The use of iodo orm in some measure undoubtedly acts as an accelerating agent to the printing process, but it is used more particularly to give a greater degree of porosity to the portions of the image which have been least exposed to light so as to make such areas more permeable to the etching solution, or more soluble if such areas of the coating are to be variably removed. In any event, I do not limit myself to the use of iodoform or to a furfural resin as any other light sensitive coating which reduces its permeability under the action of light In this connection is considered a practical equivalent, quite in cdntrast to the eil'ect of ferric chlorid on gelatin as heretofore used in photogravure. Should it be desired to use my method for rotogravurc processes, a separate screen impression can be superimposed on the continuous tone image so as to form ink retaining walls in the deepest shadows corresponding to the greatest depth of a variable relief medallion. As a substitute for the geometrically ruled screen, referred to above, any form of irregular grained texture screen may be used, or the plate. itself may be dusted over with powdered resin sufiiciently scattered to leave open areas between the powdered particles to form a grain.

Reference has been made hereinbefore to the desirability of having an image intended for medallion etching composed of isolated areas or dots, such for .instance as when an original is made with charcoal on grained paper so as to secure a stipple effect. In addition the original may be made by means of the air brush and the negative or positive by using a half tone screen and lastly print-j ing such a half tone on my coating with the image slightly out of focus. This also produces a stipple effect causing the coating to become more permeable because of being thinner at the stipple points which facilitates the beginning of the'variable action of the etching solution. I do not limit myself to the use of any accessory steps since the broadest feature of my invention is independent of such details however adaptable they may be in meeting various practical exigencies.

.VVhat I claim is:

1. The process of variable relief etching,

consisting in covering a metallic surface with a light-sensitive coating, in subjecting the same to a luminous image to produce selectively variable permeable areas in the coating comparable to the lights and shades of the image, in subjecting the image impressed coating to a single mordant, and in selectively controlling the variable rate of action of the mordant by means of the variable image areas.

2. The process of variable relief etching, consisting in covering a metallic surface with a light-sensitive coating, in exposing the same to a luminous image to selectively form areas of low and high permeability corresponding to the lights and shades of the image, and in variably subjecting the coating and its supporting surface to the action of an etching agent.

3. The process of variable relief etching,-

face to a single etching solution so as to produce a variable relief on said surface.

4. The process of variable relief etching, consisting in covering a suitable surface with a light-sensitive coating, in exposing the coating to a luminous image to thereby produce areas of variable permeability, and in variably subjecting the coating and surface to an etching. solution so as to etch the surface deeply corresponding to the more permeable parts of the image and only slightly or not at all corresponding to the variably luminous parts of the. image.

5. The process of variable relief etching, which consists in forming image areas in a suitable coatingof low permeability and inter-related areas of high permeabilit and in translating such areas into a variab e relief metallic surface by variably subjecting the same to an etching agent'whose rate of action is dependent on the variable permeability of the image impressed coating.

6. The process of variable relief etching, which consists in covering a suitable surface with a light-sensitive coating, in subjecting said coatlng to a luminous image composed variable relief corresponding to the lights and shades of the image.

In testimony whereof I affix my signature.

MURRAY C. BEEBE. 

